This invention relates to a means for trim balancing the low turbine shaft of a jet engine and, more particularly, the invention is concerned with providing a balance weight which can be inserted into a hollow turbine shaft and clipped to a support member therein in the proper position without disassembling the engine.
Jet engines are said to be comparatively free of vibration. Occasionally, however, vibration is noticed during operation. If it is excessive, the cause must be located and eliminated because vibrations can become dangerous under certain conditions and cause undue wear of operating parts.
Ordinarily, the operational check for engine vibration requires that an engine be operated while a vibrometer is placed against it in several places, usually over the compressor, turbine wheel and the bearing housings. The degree of vibration may be read directly from the vibrometer, after which the engine is shut down. When excessive vibration is noticed, the engine is usually scheduled for overhaul.
The excessive vibration is generally produced by an unbalance somewhere in the rotating system causing the shaft to whip sideways and with possible damage to the engine. Overhauling the engine to correct the unbalance is a tedious and time consuming procedure. It would be much more desirable if the unbalance could be corrected by a simpler and easier procedure which would not require any substantial disassembly of the engine.